Investigation of force relaying elastic elements in the Drosophila melanogaster bona fide mechano-electrical channel NOMPC

Background Hearing in Drosophila requires the NOMPC (TRPN1) channel. NOMPC is a mechano-electrical transduction (MET) channel whose amino-terminal ankyrin repeat (AR) domain consists of 29 ARs, that assemble into a helical structure, tether the channel intracellularly to microtubules, and are essential for channel mechanosensitivity. Based on these data, the AR domain was implicated as the “gating spring”, an elastic element relaying forces to the channel gate.

Methods We used Laser-Doppler-Vibrometry and simultaneous compound action potential recordings to assess the hearing performance and MET channel gating of adult flies in vivo. We performed in vitro experiments, recording spontaneous single channel currents and stimulated channel activity in outside-out patches of NOMPC29+29ARs and NOMPC expressing S2 cells. S2 cells do not natively express NOMPC and are mechanical insensitive.

Results Consistent with previous data, NOMPC29+29ARs enabled mechano-activated currents in S2 cells, its mechanosensitivity closely resembled those of normal NOMPC in vitro , as did sensitive hearing in vivo. Also, the NOMPC-dependent nonlinear gating was found unaffected. Hence, duplicating the AR domain neither affects NOMPC mechanosensitivity in vitro nor in vivo. Manipulations of other channel elements, however affected parameters attributed to the gating spring.

Conclusions Investigation of other channel structures revealed findings that suggest an elastic element in close proximity to the channel gate. Such an element would reduce the mass and friction that would have to be overcome during channel gating and thus allow the channel gate to more readily change states. Here we present a candidate for such an elastic element that could also be termed a gating spring.

Supported by DFG, SFB889, A1

Publication History

Article published online:
12 May 2023